The invention relates to an apparatus for automated respiration, for example in the CPAP (continuous positive airway pressure) therapy and in the biPAP (biphase positive airway pressure) therapy. In the CPAP therapy, a positive air pressure is continuously exerted onto the airways; wherein a pneumatic fixation of the upper airways is achieved and an obstructive respiratory disturbance (sleep apnea respiratory standstill during sleeping) should be avoided. In the biPAP therapy the pressure is exerted intermittently. In both cases, the pressure level is individually adjusted to the patient.
In positive pressure respiration the positive airway pressure is used either continuously (continuous positive airway pressure: CPAP) or intermittently (biphase positive airway pressure: biPAP) via a nose mask or nose-mouth mask. This type of therapy is based on the concept that due to a pressure of 5 to 25 mbar the airways in the pharynx can be kept open and that the patient can thus inhale and exhale without hindrance. However, since the CPAP or biPAP apparatuses existing so far do not measure the respiratory gas flow, there is the risk that an applied respiration pressure is not linked with a normal respiratory flow. Since the respiratory flow is not measured directly, complicated diagnostic methods have to be used to document the effectiveness of the respiration therapy (polysomnographic diagnosis and adjusting the respiration therapy over several nights in a sleep laboratory). At present, no CPAP/biCPAP apparatus is known which measures simultaneously quantitatively the respiratory gas flow and the obstruction of the airways.
It is known that there is a critical pressure for a collapse of the upper airways. For example, from CHEST, Vol. 110, pages 1077-1088, October 1996, and Sleep, Vol. 19, No. 10, pages 184-188 it is moreover known to avoid sleep apnea by means of a CPAP therapy in which a positive air pressure above the critical pressure is continuously supplied to the patient during sleep. In this case it is assumed that the critical pressure is assessed for each patient prior to the therapy. Moreover, it is intended to measure the critical pressure after the treatment in order to evaluate the success of the therapy. Moreover, it is known from the prior art to determine the critical air pressure as an intersecting point between a straight line through measuring values of the maximum respiratory gas flow at different positive air pressures, said values being inserted into a diagram above the positive air pressure, and the axis of this pressure.
1 Translator""s note: Error in the original German text: should read xe2x80x9cNo. 10xe2x80x9d
The required effective CPAP pressure, e.g. in a CPAP respiration apparatus, is not a constant value but varies in accordance with the body position, the sleeping phase and changes in the body weight or if alcohol is consumed or medicines are taken. The effective respiration pressure thus depends on different factors. CPAP apparatuses known so far are not able to modify the effective respiration pressure in accordance with these factors. For example, it is known that most patients need a higher effective respiration pressure when lying on their backs than when being in a lateral position. The reason therefor resides in that the critical collapse pressure and the airway resistance change in accordance with the above factors. The known CPAP apparatuses cannot measure the airway resistance and the collapsibility. In order to nevertheless guarantee an effective respiration during the entire period of sleep, the effective respiration pressure is as a rule adjusted at a higher value than would be necessary. Thus, the effective pressure is adjusted such that there is no respiratory disturbance if the patient lies on the back. However, if the patient always sleeps in a lateral position, this means that during the entire night the patient is supplied with a too high respiration pressure.
Thus, it is a disadvantage of the prior art that individual breathing changes of a patient caused, for example, by occurring snoring, body position changes, sleep phase changes, consumption of alcohol or health disturbances during the therapy cannot be taken into consideration.
In contrast thereto, it is the problem of the invention to provide an improved apparatus for automated respiration.
In solving this problem, the invention is based on the principal idea of continuously measuring the respiratory gas flow in the apparatus during respiration and examining for an obstructive airway disturbance.
Thus, the invention can essentially serve two purposes: On the one hand, an automation of the CPAP or biPAP adjustment and, on the other hand, an automatic adjustment of the effective CPAP or biPAP pressure to individual changes of the mechanics of breathing, for example caused by changes in the body position during sleep.
When initiating a nasal respiration therapy, the initially adjusted respiration pressure is modified by the invention in accordance with the measured respiratory gas flow. The initial respiration pressure (Pn=k) is given by the doctor. The threshold value for normal respiratory gas flow is also given by the doctor. Both values are inputted into the apparatus. On the basis of both values (Pn and respiratory gas flow threshold value) the invention can automatically change the nasal respiration pressure to such an extent that the patient does no longer have any respiration disturbances and has a normal respiratory flow.
It is the advantage of the invention that the respiratory gas flow and the airway obstruction (Pcrit, airway resistance, flow limitation) are measured continuously, and the positive air pressure is modified accordingly. It is thus possible to treat the patient with a lower respiration pressure, e.g. during respiration at home. It is a further advantage of the present invention that, for example during respiration at home, an effective respiration pressure with normal respiratory flow is guaranteed at any time.